Device for indicating the true shape of workpieces



Jan. 22, J. w CARDER "DEVICE FOR INDICATING THE TRUE SHAPE OF WORKPIECES' Filed Aug. 15, 1949 SSheets-Sheet l Fig.3.

Inventor James m Carder Jan 22, CARDER 2,583,253 I DEVICE FOR INDICATING THE TRUE SHAPE OF WORKPIECES Filed Aug. 15, 1949 5 Sheets-Sheet 2 Fig.6.

3 James W Carder INVENTOR.

Jan. W CARDER DEVICE FOR INDICATING THE TRUE SHAPE OF WORKPIECES Filed Aug. 15, 1949, 5 Sheets-Sheet 3 u'mw W. Carder INVENTOR.

Patented Jan. 22, 1952 Davide i oainmo 'rmaTHE TRUE sneer. or WORKPIECES' iames Wa d Sal m V Application August 15, 1949, Serial No. 110,401

This invention relates to testing and indicat ing devices of the type indicating the deviation of the surface of a work piece from true shape as described in my earlier co-pending application Serial No. 778,345, and it has for its object to provide a device indicating deviations from the true shape of work pieces which are in the process of being machined and" also indicatingthe location of the deviation and the extent to which the deviation is reduced during work;

Testing, gauging and centering" devices using electric light indicators are knownin the art but most indicators merely serve the purpose to indicate the fact that the suriace of the workpiece or its center deviates from the true shape" or from the true center, but leaves it to the operator to determine the location of the irregularity and the extent of such irregularity. v

In the above referred to earlier application Serial No. 778,:345 an indicator wasd'e's'cribed operating by means of an adjustablefeeler through which a current is flowing. H

l'he object of the invention is an improvement of said testing and indicating devices as hitherto used, resulting in the removal ofall guesswork when setting up the work piece in the machine tool, in the removal of all eye strain and fatigue, and in the truing of a work piece with an accuracy which has not been possible'in kno'wn ar rangements.

A further object of theinvention consists in an improvement of the indicating device as described in the above mentioned earlier applica; tion Serial No. 7*?6345 resultin'gin the reduction of the weight and size of the indicator, in the elimination of a large number of moving parts, in connections which are inoreeasily adaptable for A. (3. operation, in a noiseless operation arid in a reduction of the current consumption; the latter being of importance in connection with portable apparatus.

The main advantage of the improvement described in the following specification-resides in the fact that the accuracy of the indicator according to the invention is not only much" greater than that of mechanical or electromagnetical indicators, but that it also exceeds by farth-at of the mechanical precision tools customarily used in such work for determining thecorrect shape, so that the apparatus according to the inven-tion cannot only be considered as a means for the rapid indication of deviations or aberrations from the rue shape which could'also be indicated by means of precision instruments, butthe indicator forms itself a measurinedeviaa within 7 claims; (01. 33-469).

latter is kept at definite potential.

v .2 a certain range of precision which is not covered by any other instrument which may be used by a skilled operator even when spending much time for a measurement.

A further main advantageof the invention consists in the fact that the-currents passing through the feeler or probe arm are practically negligible so that neither relays nor a reduced voltage need be employed for reasons of safety.

According to the present invention the indicator comprises a probe arm or feeler forming part of an electric circuit completed by the work piece, a locator switch consisting of a number of contact segments arranged in a circle and a rotating contact arm, which contacts a segment corresponding to a zone on the work piece in contact with the probe arm or feeler, a series or electronic tubes each of which is associated with one of the contact segments and a number of inclicating glow lamps on an indicator panel each controlled by one of the electronic tubes and so positioned that said lamps will illuminate a'segment of the indicator correspondingto a zone on the work piece which deviates from the true shape.

The electronic arrangement according to the invention includes means for bringing the probe arm or feeler to a definite potential when the said probe arm is in contact with the work piece and it further includes electronic tubes which operate as soon as such a potential is established in the probe arm. A number of electronic tubes, equal to the number of segments of the locator switch are set for operation whenever such a definite potential exists in the probe arm, while only the individual segment on which the rotating contact of the locator switch rests for the time-being is capable of making its tube conductive, thereby sending a current through the indicator lamp which illuminates the segment corresponding to the stretch on the work piece on which the probe arm rests. Only those indicatinglamps are therefore operative which are located in sectors of the indicating device corresponding to the location of the probe armor feel- .eronthe Work piece. Also, according to themvention, once the electronic tube has operated, it remains conductive as long as the current throughthe probe arm flows or as long as the Therefore a segment or segments of the indicator which'are illuminated by the indicator lamps indicates a pointror'zone'bn the work piece along which the probe-arm or iieeler'touches the same.

The invention is illustrated in the accompany ing drawing showing two embodiments of the same by way of example. It is however to be understood that the examples which are shown are merely illustrative and serve the purpose of explaining the principle of the invention and the best modes of applying said principle. These examples however are not to be considered as being limitative with respect to the modes of application of the principle of the invention and modifications of the examples shown in the drawing are therefore not necessarily departures from the essence of the invention.

In the accompanying drawing: I

Figure 1 is a diagrammatic plan view showing part of a machine tool and the indicating apparatus applied to and arranged in front of and near the operators stand. a

Figure 2 is an elevational partly sectional view of the transmission of motion from the spindle or shaft of the machine tool to a locator switch.

Figure 3 is an elevational side view of the indicator used near the operator's stand.

' Figure 4 is an elevational front view of the indicator.

Figure 5 is an elevational partly sectional view of the probe arm or feeler applied against the work piece.

Figure 5 is a diagram of the connections and of the electronic arrangement used for the indicating device as illustrated in Figures 1, 2

and 5.

its object to check the accuracy of a work piece which is in the process of being machined or shaped by a machine tool which is driven by a spindle or shaft II. This shaft is provided on its end with a cavity l2 which may either be cylindrical or conical. The conical shape is shown in Figure 3 and the cavity cooperates with .a conical friction plug 14 which may be inserted into it. The friction coupling member it therefore rotates with the shaft or spindle II and it drives the flexible shaft l5 which leads to the locator switch It consisting of a rotating contact arm I! (see Figures 6 and 8) sliding on a number of contact segments 18. It will be clear that the speed of rotation of the contact arm H is equal ,to the speed with which the spindle H carrying the work piece rotates, or in the event that a transmission should be inserted, is proportional to the speed of the spindle l I.

The work piece 20 is shown in the drawing as being mounted on the spindle stock of a lathe 2i which is shown partly in Figure 1. It is however to be understood that the invention is not specifically comiected with lathes or with similar machine tools and that the lathe is merely representative of some kind of machine tool in which a work piece is machined while rotating.

The accuracy of the shape of the work piece which is moved with respect to a cutting tool is currently checked by the probe arm or feeler 22 which protrudes from a sleeve which may be insulated and which is held in or mounted on a support 23 which, in its turn, is mounted on the rest of the lathe. The sleeve 25 is gripped in a suitable holder 24 permitting to hold the.

probe arm or feeler 22 and to apply it against the work piece in any desired position.

The work piece 20 is supposed to be grounded through the lathe and through the devices holding it and special precautions in order to secure grounding of the lathe may be taken.

On the side of the lathe 2! where the operator has his stand a box 26 containing the electronic tubes, switches and other electric devices is mounted, while on the opposite side of the lathe and facing the stand of the operator the indicator 30 is shown, which consists of a fiat cylindrical box 3|, covered by a front plate 32 provided with arcuate slots 33. The arcuate slots are preferably arranged in a circle and each slot covers an are which corresponds to an arcuate portion of equal or proportional extension on the work piece. Eight slots are shown in the drawing but the number is adapted to the type of work to the work piece. to the speed and to the degree of accuracy which is to be maintained. The number of slots is always equal to the number of segments I8 on the locator switch I6.

Behind the front plate the box is divided into compartments, each compartment containing a lamp bulb 35 which in the example shown is a glow lamp filled with neon but which may of course also be of any other type. Each glow lamp bulb is so arranged with respect to the slots that when illuminated it illuminates a single slot.

The entire indicating apparatus 30 is arranged in front of the operator and approximately at the height of his eyes so that it can be supervised by the operator without difficulty. The illuminated slots indicate to the operator the high spots or zones on the work piece along which the feeler 22 touches the work piece as will be explained more fully below.

The arrangement thus far described corresponds more or less to the arrangement described by earlier application Serial No. 776,345 to which reference may be had with respect to further details of the arrangement.

The present invention has mainly for its object the means for operating the indicating lamps which differ from those which have been described in the aforesaid earlier application.

The means used in the arrangement shown in the drawing consist essentially of electronic tubes which provide a degree of accuracy which is unobtainable with other means.

The electronic tubes may all be preferably of the same type and, by way of example, thyratron tubes are used which block or intercept the flow of current through the tube upon application of a negative grid bias which is below a certain value. The tube however fires or permits current flow when the grid bias is raised above said value. It is also a characteristic of the tube that once the tube has fired the current flow through the tube will persist even if the grid bias after firing is lowered a little below the grid bias voltage at which firing originally occurs. Tubes 2D21 for example correspond to this description, but it is obvious that the type of tubes used is secondary, provided a cutoff voltage is used, below which the tube is blocked and above which the flow of current through the tube is started.

In the arrangement shown in the drawing two groups of thyratron tubes may be distinguished. A probe arm tube or tubes 40 are directly asso ciated with the probe arm or feeler 22 and operate as soon as the contact between the probe arm 22 and the work piece 20 has been established. Adjustment may be made for operation before actual at the: mama-1t air-which the ground potential G of the work; piece can. be made active.v i

i A sing-lei probe tube maybe used, but in order to be. able to use; A. 6; feed lines; of a building, such as customarily available, without, any special rectifying means, it is preferable to; usetwo thyratrcn tubes 38;. 39. in a Iii-mt of; push-pull connection. The. twov controll grids: 3:1,, 31a: of the. thyratron tubes are both connectedi with the grounded grid. bias: battery: 3& omen the; grid resistance. At; the battery is so; connected. with the grids 3.1:; 31c. that; a. high, negative: grid: bias is obtained: which however; just suflicientlyhigh to block or intercept; the: flow: of. current through thertubes. The: cathodes. 42 and: therscizeem grids Off the tubes. 38;. 39 areprefe'rablyr grounded. (Gr) The-plates. 4.4; 4411: of. the. tubes-381.39 areiconenected: with the two; ends otacooil: 45 which: is center tapped at 4:6.- and which is part; of? the transformer 48 which. is' connected: with at. source of current (not shown); whichmay-he. the usual 1.10 v. A. C. feed lines:

The. transformer. 48: providing; current for the plate circuits may. also; have a further? winding 4% in. which a. low; voltage. is produced. for. the heatersof the cathodes of. thethyratrom tubes.

Thecenter 5!!v of; the coil 45isr. connected. by means of. conductors: 5-3 withia. connection point 55 which is grounded at? G2. overv the capacitySB and which. is. also connected. with a. resistance system consisting of t'wdresistances 5].; 58 one of which or both of which. may be adjustable. The two resistances 51s and 5.8. arejoined at: a junctionpoint .60. Theiresistance. 5&tis: grounded separately and directly at Ge.

The junctionipointi is connected? by conductors 6i 62 to the rotatable: switch arm. Ofi=thi1OC8t0I switch for a purpose described? below. The second group of thyratrons isformedmythezcon: trol, group 89 which consists Ofi a. numberof thyratron tubes8 .|',.82; 83;. 88iwhichniszequal to the number of; segments Hhonathe-rntata'ble locator switch. 16. The cathodessofiail the .tubes of' the. group; are; connected with; conductor: 6 which is joined-Jwitnthezrotating: arm IT. of the locator switch I63. The grids- Ei; 92,.93'. .88 ofthe tubes 34 81.33 ..8l8iares-.conneetedton one. side over individual; resistancesz'lfl: allotted to each tube and: over: a. common: conductors: 12 with connection1pointi-55; andgonitl'leother side; the said grids are?connected:withxthesegments I8 of the: locator switch, eachz. grid bieingconinected by means: of one ofjtheiconductorsa 1'9 with one of saidsegments 1 l 8.

The plates of thegthyratronztubesitl; .82.: .88 are connected with piatecircuits ID], m2, m3 H18 each ofJwh-ich:includessonemizthe indicator glow lamps 35; locatedibehind thesarcue ate slots 33 of the box 3|.- In;this-. casemeon glow lamps are. used and. one -of;th.e.ae1ectrodes: of each of said lamps is. connectediwith the; plate circuit of one of the tubes:wl ile:the-otheryelem trodes gare joined. to a common ground conductor is (grounded at G4). v

The heater of the gcathode; iof the tube 1. .8 B3... .88 are supplied. by-conductors.63',- 65 in themanner above explained-..

The operation ofthe-.arrangement,is the-'fole lowing: Referring first to the operatorsitruing operation ,let it be, assumed that ;the workupiece has a high spot and thus deviates from the true hsPs--- T e-pr b s morieeler ia-i sues: pu h contact.- with the feelen progresses more-slotsare illuminated and: the

betweentthe probearm: and the monkpieea atthe high spot, while; the spindleand' thenworkr piece rotate at their normat.speed.-. The contact between feeler and work: piece lights the; lamp bulb work is finishedi when all; the? slots are illum-hnated. Even a slightioutwaazd movement; of the probe: arm or ieeler-"flqtherr causes all; the bulbs togoout.

. During this-operation the electronic armnge ment operates: as: follows.

A contact betweenife'el'en 22 and; workpiece: 2i! puts ground potential; on: the:-.-feeler 22: and on conductor 59: connected; with. it; This also; con P- nects; a groundpotentiaLwith-a grids 31 ,.371'11 which is less negative: than the:- gridibias potentialr provided by the battery 36.- Therefore: thetubes'ii'e, 3Q fire wheneveraipositiver halt? wave passes one of the tubess38",, 39. Thisepassase of tliefposirtive half' wave occurs at? the: proper intervals when'the coil E5 is energized from-'thenetworkby means? of. transformen 48a the current: flows through the-thyratronptubes only'imoneedirection and as the tubes. 38;, 393 thus act. as". rectifiers, point 5!! on coil 35 receivesi-asdefiniteili): C.'.'po.=- t'ential which is. alsota ppliedzto point. 55.. This point is connected with .the'griiis.9;li.;92;.93 9B of the thyratron. tubes 821, case I 88. through the resistances. 1.0. Across: the. resistance: 51' and by; means; of adjustable. resistance- 58' a voltage is developed at. point. 6:0: which: islesss negative than the voltage applied to;theiigrids and which is.) also, applied" to cathodes of'the tubes: 81,. 82, 83 88.v

At the moment-.atvwhicli thelzfeeierrZZ touches the work. piece 20.5 and. operates the: thyratron tubes 38; 39;. the; rotating. arm I11 of. the. locator switch I6 is one. definite: segment: say on: segment I812 of: the switchilfii It i'sitliencseeri'zthat by means of; conductors 6! and; 62;. the: switch arm l1: and thesegment b 'ofsgroupo l8; and by means of conductors. T921. the: grid? 98. of tube.- 88 is supplied 1 with. a. less negative"; voltage. than. the one applied: to:- the: other; thyratron tubes. 82!, 8-2

8-1. I11 v has ofi'courseibeenassumedthat the voltage which has: been;v applied to point- 55 will be sufficiently negativerto.preventtubes from firing; When the- 1ess--' negative. voltage: of :point til'is now applied-to the -grid:9 8 of;tube. 88-,,the tube fires and lights lamp 35b;o.f;the,lamp. group 35 which is located behindi-slots; 33b of; the-:group of slots 33.

, It will be understood that when tbeiprobe :arm or feeler 22 touches the worlepiecedd this will be immediately indicated 011; th indicator circuit. The energization-oi thexglow'laznp 35 is relatively permanent and it; lasts as long as. the

feeler touches the; work-pieces Whem, fonin-zstance, the feeler 22 touches the work piece along an arc of 1803 1amps-.a,-..b c-;- diof; the:lamp group 35 light up and stay lighted together; and: the thyratronsv remain conductive, once they. have been fired.

. ni emroh arm on eel ri. meet uteof u h w th.thelworlapiec imtbegsiowv ampsmne a ain ext nsi ished;z

Numbers or other markings such as the numbers 1, 2, 3, 4 shown on the dial or front wall of the indicator assist in locating the spot or zone of deviation from true shape relatively to the position of the test prod.

It will also be understood that the device as described may be used to check the balanced condition of a body of rotation for example and to detect any eccentric position of the center of gravity with respect to the axis of rotation. Such an eccentric position of the center of gravity entails vibrations of the body of rotation while rotating, and the test prod by suitable adjustment maydetect such vibrations, as in this case, when properly adjusted, it does not come into contact with the surfaces of the body of rotation when the latter is at rest or is rotated slowly while contacting the said body during a rotation which produces such vibrations. This condition may therefore bereadily and directly detected on the dial of the indicator.

The arrangement according to the invention has the major advantage that it can be introduced into a portable apparatus of the size of a portable radio apparatus. This modification is shown in Figures 7 Y and 8.

The portable apparatus consists of a small portable box I provided with a handle I2I into the front wall of which the indicator 30, such as above described, is built in. The front wall may also be provided with a switch I22 for controlling the current supply and with a jack I25 into which the plug I26 connected by a cable I2! with probe arm or feeler 22 is inserted.

The rear wall carries the rotary locator switch 1*:

I6 and the flexible shaft I5 which drives the switch arm and which is attached in the manner which has been described before, the flexible shaft coupling I28 permitting to connect different coupling members with the same.

The coupling member which is shown in Figure 7 consists of a threaded screw spindle on which the coupling member consisting of two rubber wheels I32 is mounted. The rubber wheels I32 may be inserted into any cylindrical cavity of a spindle or shaft in order to establish a coupling of the flexible shaft I5 with said spindle or shaft. The rubber wheels are compressible by means of nuts I33 on the threaded screw spindle and by means. of a spacer sleeve I arranged between said wheels. Pressure may be exerted, changing their diameter, so as to fill cavities approximately of the size of the wheels, with the latter being coupled by the pressure exercised in a radial direction.

In the interior of the box I20 the tubes 38, 39, 8!, 82, 83 83 and the transformer 48 togetherwith the condensers, resistances and other units are arranged.

Deviations of the work piece from its true shape of an extent which is not measurable by the usual measuring tools may be detected by the indicating apparatus.

It will be understood that the apparatus has been described specificially but that a number of changes may'take place without departing from the invention defined in the annexed claims.

Having described the invention, what is claimed as new is:

1. A device for testing the true shape of work pieces and for indicating deviations from said shape, comprising means for rotating said work piece, a'prob'e arm contacting said work piece, a probe circuit closed by the contact between probe Iii arm and work piece, an indicator, including a number of indicating lamps, each lamp corresponding to a section of the work piece, a locator switch with a rotating arm and segments, said armbeing moved over said segments at a speed proportional to the speed of the work piece and being connected with the probe circuit and energized during rotation of said work piece when the same comes in contact with the probe arm and means for maintaining one or more indicator lamps operative during the entire period of contact between said probe arm and said work piece, each of said means being connected with one of the segments of the locator switch.

2. A device for testing the true shape of work pieces and for indicating deviations from said shape, comprising means for rotating said work piece, a probe arm contacting said work piece, a probe circuit closed by the contact between probe arm and work piece, an indicator, including a number of indicatin lamps, each lamp correspondin to a section of the work piece, means for operating said indicator lamps in succession, said means including a group of electronic tubes the number of which is equal to the number of indicator lamps, control circuits for said electronic tubes, each indicator lamp being controlled by one electronic tube of the aforesaid group, a locator switch with a number of segments equal to the number of electronic tubes of the aforesaid group,'each locator switch segment being connected with the control circuit of one of the electronic tubes, said switch being further provided with a rotating contact arm moved over said segments at a speed proportional to the rotational speed of the work piece and coupled with the means for rotating the work piece, said contact arm being connected with a further portion of the control-circuit, the voltage of which is controlled by the flow of current in the probe circuit.

3. A device for testing the true shape of work pieces and for indicating deviations from said shape, comprising means for rotating said work piece, a probe arm contacting said work piece, a probe circuit closed by the contact between probe arm and work piece, an indicator, including a number of indicating lamps, each lamp corresponding to a section of the work piece, means for operatin said indicator lamps in succession, said means including a group of electronic tubes with control grids, the number of tubes being equal to the number of indicator lamps and each lamp being controlled by one tube of the group, means for controlling the operation of all the tubes controlled by the probe arm and means for controlling each individual electronic tube upon first contact of the probe arm with the section corresponding to the lamp, said means including a locator switch, with a rotating contact arm, coupled with the means for rotatin the work piece and with a number of segments. each connected with the control grid of one of the tubes, each of said segments corresponding to one zone of contact of the probe arm with the work piece.

4. A portable apparatus according to claim 3, comprising a casing containing the electronic tubes, said casing including a front wall carrying the indicator, a rear wall carryin the 10- cator switch, and a flexible shaft for connecting said switch with the means for rotating the work piece.

5. A device for testing the true shape of work pieces and for indicating'deviations from said shape, comprising means for rotating said work piece, a probe arm mounted near the work piece for contact with the same, means for imparting a definite potential to said probe arm when in contact with the work piece, a first group of electronic tubes connected with said probe arm and controlled by the potential imparted to the same, a rotatable locator switch, including a rotatable contact arm, coupled for rotation with the means for rotating the work piece, and further including a number of contact segments, a control group of electronic tubes, with a number of tubes equal to that of the contact segments, the operation of the tubes of said group being controlled by the first group of electronic tubes connected with the probe arm and the operation of an individual tube within the control group being controlled by the locator switch, and a group of indicating lamps indicating contact of the probe feeler with the work piece, each indicating lamp being controlled by one of the electronic tubes of the control group.

6. A device for testing the true shape of work pieces and for indicating deviations from said shape, comprising means for rotating said Work piece, a probe arm, mounted near the work piece for contact with the same, means for imparting a definite potential to said probe arm when in contact with the work piece, a first group of electronic tubes provided with a control grid connected with said probe arm, said tubes being rendered conductive by the application of the probe arm potential, a rotary locator switch consisting of a rotating contact arm and of a number of contact segments, the rotating contact arm being coupled for rotation with the means for rotating the work piece, a further indicator controlling group of electronic tubes with control grids, adapted to be rendered conductive upon application of a predetermined potential, each control grid of the last named indicator controlling group being connected with the first named group connected with the probe arm by means of a common conductor and with one of the segments of the locator switch, the former connection providing a potential at which the tube remains operative once it has started to operate and the latter connection providing a potential at which the tube starts to operate, a number of indicator lamps equal to the number of segments on the locator switch and means to control each of said indicator lamps by an electronic tube of the said further group of electronic tubes.

'7. A device for testing the true shape of work pieces and for indicating deviations from said shape, comprising means for rotating said work piece, a probe arm mounted near the work piece for contact with the same, means for imparting a definite potential to said probe arm when in contact with the work piece, a first group of electronic tubes provided with a control grid connected with said probe arm, said tubes being rendered conductive by the application of the probe arm potential, means for supplying the said electronic tubes with current, a common output and supply circuit for said group of tubes, means to develop a constant potential within said output and supply circuit, a rotary locator switch including a rotating contact arm; coupled with the means for rotating the work piece, and further including a number of contact segments, a further indicator controlling group of electronic tubes with control grids, adapted to render the tube non-conductive upon application of a predetermined cut-ofi potential, and of rendering it conductive upon application of a higher potential, the number of the electronic tubes in said group being equal to the number of segments of the locator switch, means connected with the output and supply circuit of the probe arm group of electronic tubes for applying a potential, developed in the aforesaid circuit, to all the control grids of the electronic tubes of the indicator controlling group of tubes, means for keeping said potential at a cut-ofi value before the operation of the electronic tubes has started and at a value at which the tube will be conductive after starting, a connection between each segment of the locator switch and the control grid of one of said electronic tubes, said connection forming part of a circuit including the rotary arm of the locator switch and closed when the said arm touches a segment for applying a potential on the control grid of an electronic tube of the indicator controlling group rendering the group conductive, output circuits for each of the aforesaid electronic tubes and indicating lamps controlled by said output circuits, the lamps being lighted successively upon contact of the probe arm with the work piece along a section corresponding to the zone of contact and said lamps r remaining operative as long as such contact between probe arm and work piece lasts.

JAMES W. CARDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,040,715 Mann Oct. 8, 1912 2,090,803 Moore Aug. 24, 1937 2,123,443 Taylor July 12, 1938 2,316,524 Martin Apr. 13, 1943 

